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Основы программирования на
Java. Программирование для
Android
Android: Введение
Кузнецов
Андрей Николаевич
Санкт-Петербургский Государственный
Политехнический Университет
13.02.2013
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Инструментарий Разработчика
• Android SDK r21
– http://developer.android.com/sdk/index.html
• Eclipse IDE for Mobile Developers
– http://eclipse.org/mobile/
• ADT Plugin для Eclipse
– https://dl-ssl.google.com/android/eclipse/
• Java SE Development Kit 7
– http://www.oracle.com/technetwork/java/javase/
downloads/jdk7-downloads-1880260.html
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Android SDK (1)
• SDK Tools (<sdk>/tools/)
– Contains tools for debugging and testing, plus other
utilities that are required to develop an app.
• SDK Platform-tools (<sdk>/platform-tools/)
– Contains platform-dependent tools for developing and
debugging your application. These tools support the
latest features of the Android platform and are
typically updated only when a new platform becomes
available.
• Documentation (<sdk>/docs/)
– An offline copy of the latest documentation for the
Android platform APIs.
See http://developer.android.com/sdk/exploring.html
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Android SDK (2)
• SDK Platform (<sdk>/platforms/<androidversion>/)
– There's one SDK Platform available for each version of
Android. In order to build an Android app, you must
specify an SDK platform as your build target.
• System Images (<sdk>/platforms/<androidversion>/)
• Sources for Android SDK (<sdk>/sources/)
• Samples for SDK (<sdk>/platforms/<androidversion>/samples/)
• Android Support & Google APIs
See http://developer.android.com/sdk/exploring.html
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Android SDK Tools
• Android
– Lets you manage AVDs, projects, and the installed components of the
SDK.
• Dalvik Debug Monitor Server (ddms)
– Lets you debug Android applications.
• Android Emulator (emulator)
• Monkey
– Runs on your emulator or device and generates pseudo-random
streams of user events such as clicks, touches, or gestures, as well as a
number of system-level events.
• Monkeyrunner
– Provides an API for writing programs that control an Android device or
emulator from outside of Android code.
• И многое другое ...
See http://developer.android.com/tools/help/index.html
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Android SDK Platform Tools
• Android Debug Bridge (adb).
– Android Debug Bridge is a versatile tool that lets you
manage the state of an emulator instance or Androidpowered device. You can also use it to install an Android
application (.apk) file on a device.
– The Android SDK provides additional shell tools that can be
accessed through adb, such as bmgr and logcat.
• The other platform tools, such as aidl, aapt, dexdump,
and dx, are typically called by the Android build tools
or Android Development Tools (ADT), so you rarely
need to invoke these tools directly. As a general rule,
you should rely on the build tools or the ADT plugin to
call them as needed.
See http://developer.android.com/tools/help/index.html
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Архитектура ОС Android
See http://www.android-app-market.com/android-architecture.html
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Linux Kernel
• The basic layer is the Linux kernel. The whole Android OS is built on
top of the Linux 2.6 Kernel with some further architectural changes
made by Google. It is this Linux that interacts with the hardware
and contains all the essential hardware drivers. Drivers are
programs that control and communicate with the hardware. For
example, consider the Bluetooth function. All devices has a
Bluetooth hardware in it. Therefore the kernel must include a
Bluetooth driver to communicate with the Bluetooth
hardware. The Linux kernel also acts as an abstraction layer
between the hardware and other software layers. Android uses the
Linux for all its core functionality such as Memory management,
process management, networking, security settings etc. As the
Android is built on a most popular and proven foundation, it made
the porting of Android to variety of hardware, a relatively painless
task.
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Libraries
• The next layer is the Android’s native libraries. It is this layer that enables
the device to handle different types of data. These libraries are written in c
or c++ language and are specific for a particular hardware.
• Some of the important native libraries include the following:
• Surface Manager: It is used for compositing window manager with offscreen buffering. Off-screen buffering means you cant directly draw into
the screen, but your drawings go to the off-screen buffer. There it is
combined with other drawings and form the final screen the user will see.
This off screen buffer is the reason behind the transparency of windows.
• Media framework: Media framework provides different media codecs
allowing the recording and playback of different media formats
• SQLite: SQLite is the database engine used in android for data storage
purposes
• WebKit: It is the browser engine used to display HTML content
• OpenGL: Used to render 2D or 3D graphics content to the screen
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Android Runtime
• Android Runtime consists of Dalvik Virtual machine and Core Java libraries.
• Dalvik Virtual Machine
• It is a type of JVM used in android devices to run apps and is optimized for
low processing power and low memory environments. Unlike the JVM, the
Dalvik Virtual Machine doesn’t run .class files, instead it runs .dex files.
.dex files are built from .class file at the time of compilation and provides
hifger efficiency in low resource environments. The Dalvik VM allows
multiple instance of Virtual machine to be created simultaneously
providing security, isolation, memory management and threading support.
It is developed by Dan Bornstein of Google.
• Core Java Libraries
These are different from Java SE and Java ME libraries. However these
libraries provides most of the functionalities defined in the Java SE
libraries.
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Application Framework
• These are the blocks that our applications directly interacts with.
These programs manage the basic functions of phone like resource
management, voice call management etc. As a developer, you just
consider these are some basic tools with which we are building our
applications.
• Important blocks of Application framework are:
• Activity Manager: Manages the activity life cycle of applications
• Content Providers: Manage the data sharing between applications
• Telephony Manager: Manages all voice calls. We use telephony
manager if we want to access voice calls in our application.
• Location Manager: Location management, using GPS or cell tower
• Resource Manager: Manage the various types of resources we use
in our Application
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Applications
• Applications are the top layer in the Android architecture and this is
where our applications are gonna fit. Several standard applications
comes pre-installed with every device, such as:
• SMS client app
• Dialer
• Web browser
• Contact manager
• As a developer we are able to write an app which replace any
existing system app. That is, you are not limited in accessing any
particular feature. You are practically limitless and can whatever
you want to do with the android (as long as the users of your app
permits it). Thus Android is opening endless opportunities to the
developer.
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Программные Компоненты Android
•
•
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Activities
Services
Content Providers
Broadcast Receivers
Intents
As a developer we need only to call and extend
these already defined classes to use in our
application.
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Activities
• Class: android.app.Activity
• “An activity is a single, focused thing that the
user can do. Almost all activities interact with
the user, so the Activity class takes care of
creating a window for you in which you can
place your UI” - http://developer.android.com
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Services
• Class: android.app.Service
• “A Service is an application component representing either an
application's desire to perform a longer-running operation while not
interacting with the user or to supply functionality for other applications
to use” - http://developer.android.com
• Example: music player application.
• All Android services are implemented as a subclass of Service class defined
in Android SDK.
• There are two types of services in Android:
• Unbound Services
• Its a type of service which is not bounded to any components. Once started, it will run in
the background even after the component that started the service gets killed. It can be
run in the background indefinitely and should stop by itself after the operation its
intended to carry out is completed.
• Bound Services
• Its bound to other components and runs only till the component to which it is bounded
runs.
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Content Providers
• “Content providers are one of the primary building
blocks of Android applications, providing content to
applications. They encapsulate data and provide it to
applications through the
single ContentResolver interface. A content provider is
only required if you need to share data between
multiple applications.” - http://developer.android.com
• Example: the contacts data is used by multiple
applications and must be stored in a content provider
• If you don't need to share data amongst multiple
applications you can use a database directly
via SQLiteDatabase.
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Broadcast Receivers
• Class: android.content.BroadcastReceiver
• Broadcast receivers are one of Android
application components that is used to receive
messages that are broadcasted by the Android
system or other Android applications.
• Examples:
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Warning that the battery is getting low
Screen turned off
Change of time zone
The camera has been used to take a picture
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Intents
•
•
•
Class: android.content.Intent
“An intent is an abstract description of an operation to be performed. It can be
used with startActivity to launch an Activity, broadcastIntent to send it to any
interested BroadcastReceiver components,
and startService(Intent) or bindService(Intent, ServiceConnection, int) to
communicate with a background Service.” - http://developer.android.com
Examples:
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•
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invoke a new activity from your current activity
start other application from your activity
By firing an intent, you are telling the Android system to make something happen.
There are two types of Intents in Android:
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Explicit Intents:
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Implicit Intents:
•
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In explicit Intent, we are highly specific. We specify which activity should get active on receiving the
intent. These are usually used for application’s internal communications.
In implicit Intent we are sending a message to the Android system to find a suitable Activity that can
respond to the intent.
Example: send an e-mail
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Жизненный цикл Android Activity
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Eclipse IDE
• DEMO
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Список Источников
• http://developer.android.com
• http://www.android-appmarket.com/android-architecture.html
• http://www.android-appmarket.com/android-applicationcomponents.html
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